How to Build a Quiet Computer

Like it says – RoboTech (Lee Garbutt)


The purpose of this guide is to illustrate two examples of how to build a quiet computer that also provides above average cooling. It is written with the “first time” builder in mind. If you have the money and want to buy a Cooler Master or Lian Li case as a starting point, go for it. But if your budget is limited, there are dozens of good generic mid-tower cases available for less than $50.

Pick a case that best meets your needs (size, features, styling, cost, etc.) and then follow along. You should be able to apply these same basic principles to most any case you choose.


The three systems I’m using as examples are Socket-A, AMD Athlon CPU based computers with GeForce3 or 4 video cards. This combination of hardware is known to run warm, so it will make for a good test. These same techniques can be used for a Pentium based system as well, especially if you are overclocking that new P4.

The best time to add fans and perform other case modifications is in the beginning, before anything is installed in the case. You definitely don’t want metal shavings getting into all your high-tech goodies. Plan ahead – or if you have to disassemble an existing PC to cut holes in the case, just do it.

Fans are the primary source of noise in most air-cooled PCs. Fans are also what help keep all the parts cool. Often, a newer well-cooled case is noisy, but it doesn’t have to be. For this project, I attacked the noise issue in three main areas:

  1. Case fans
  2. CPU heatsink fan (HSF)
  3. Power supply unit (PSU)

Note: Some other potential sources of noise are the HDDs, chipset and video card fans. For my purposes, these are all within acceptable limits.

Quiet is a relative term. What seems quiet to me may or may not seem quiet to you. I am defining quiet as below 30 dBA for any single component and below 40 dBA for the completed system. For a comparison, many customized cases with multiple high speed fans will register in the mid 50 dBA range or higher. (Remember, a 3 dBA increase in sound pressure level is just detectable while a 10 dBA increase will be perceived as twice as loud.)

Now I’m not saying these rigs will be silent – just nice and quiet. Air-cooling does have its limits. The finished result will ultimately depend on the actual mix of parts you choose to use and your ambient room temperature.

Lets take a closer look at our three key noisemakers… and our solution to each problem!

RoboTech (Lee Garbutt)


1 – FANS: The most common case fan sizes are: 80mm, 92mm and 120mm. There are dozens of models with different speeds, airflows and noise ratings. (CPU heatsink fans are generally 60mm, or more recently, 80mm in size.)

In general, larger fans generate greater airflow (measured in CFM) and operate at slower speeds (RPM) than their little brothers. Due to lower fan blade speeds, larger fans typically generate less noise and at a lower pitch. Larger fans typically produce less air velocity and less static pressure than smaller fans do.

This can be a disadvantage when trying to mount a large fan to a small heatsink using an adapter. Most fan adapters are aerodynamically very inefficient. The larger fans just can’t push their rated airflow through a restricting adapter and therefore will usually perform less effectively than a smaller, high velocity fan with a similar airflow rating.

The approach I have taken for this project is to use multiple, low RPM fans. Panaflo 80mm L1As are a good choice. These fans do not move as much air as higher RPM fans do, so we need to use more of them. If you have the room and prefer to use 92mm or 120mm fans, that’s fine; just use the quiet L1A models.

The Panaflo line of fans are among the best at offering good air flow with minimal noise. Try to keep the airflow (air-in vs. air-out) reasonably balanced. If you plan to use filters on the inlet fans (a good idea) then compensate for reduced airflow by having more total airflow going into the case than coming out.

2 – HEATSINKS: The Thermalright AX-7 heatsink (AX-478 for Pentium 4) is a good pick right now. I chose it because it offers great performance at a reasonable price and it is designed for an 80mm fan. Many of us have learned the hard way that a high performance heatsink with a screaming 60mm fan is just too noisy. The AX-7 is relatively large, so check first to make sure your motherboard will accept it.

The fan you select to go with the AX-7 will depend on how much heat you are trying to dissipate (CPU, clock frequency and Vcore) and the average ambient room air temperature. In most cases, a Panaflo 80mm H1A fan is well suited for this job. (The H1A is rated for 40 CFM and 32 dBA vs. the L1A at 24 CFM and 21 dBA.)

I don’t recommend using a fan adapter and larger fan with the AX-7. (It can be done, it usually works, but IMHO it is not a good idea.) The AX-7 is already over AMD’s recommended weight specification. If you stack a big fan on top of an adapter, the torque generated by shock loads (moving the computer around) could cause the heatsink to shift on the CPU or the socket to break.

And as I said before, most adapters are so inefficient that you will probably realize better airflow with a 80mm fan than with a 120mm fan choked down by an adapter.

3 – POWER SUPPLIES: A standard ATX power supply may be OK for your needs, but if you want a really quiet one, you will have to look for a special “quiet” model. The Antec TruePower 430 watt PSU is a good choice. If you already have a favorite power supply that you would like to make quieter, then see my guide “How-to Silence That Noisy Power Supply” for details.

Some of the newer power supplies on the market incorporate variable speed fans in an attempt to make their PSU quieter. At low power levels, the fan runs slow but at higher operational current loads, the internal PSU temperature increases causing the cooling fan to speed up and be noisy.

Another one of my favorite PSUs is the PC Power & Cooling Silencer 400, which falls into this category. It is very quiet at low power levels but becomes noticeably louder at high loads. One final note on power supplies: IMHO don’t try to save a few bucks on a bargain or underrated unit, which could put your entire system at risk.

RoboTech (Lee Garbutt)

Tools and Parts

Here is a list of the tools and parts I used to build the three different computers described in this article. The cases are all about the same size, use similar motherboards and the same processors. Two of them were specifically designed to run cool and quiet. The third is one of my older “typical” air-cooled systems, used for comparison.

This does not mean you have to use only these parts or these tools. If you have some experience and know what you are doing, great! Make substitutions. If however, this is your first time around, just follow along and you should finish up with results close to mine.

Tools that I used:

  • 80mm, 92mm and 120mm hole saw (Starrette)
  • Electric drill (3/8” Milwaukee), Drill press (1/2” Craftsman)
  • 11/64 and 3/16” drill bit
  • Deburring tool, 80 grit wet/dry sandpaper
  • 12” machinist square
  • C clamps – various sizes

Now let’s look at the three different computer systems: The first two were designed to run cool and quiet, while the third rig exhibits great case and component cooling but isn’t exactly quiet. It represents a more typical high performance air cooled PC.

Cool & Quiet System # 1:

  • (1) Lian Li PC60-USB aluminum mid-tower case
  • (4) Panaflo 80mm L1A case fans 2 front and 2 back)
  • (2) Panaflo 120mm L1A case fans (1 side and 1 top)
  • (1) Modified PC Power & Cooling – TurboCool 425 watt PSU
  • (1) Thermalright AX-7 heatsink with Panaflo 80mm H1A
  • (1) Epox 8KHA+ with XP-1800+ @ 1610 MHz

Note: The PC Power & Cooling Turbo-Cool 425 watt ATX power supply that I used for this system was modified by replacing the single stock 80mm fan with two 80mm Panaflo L1A fans, one in the front and one in the back. See “How-to Silence That Noisy Power Supply” for details.


Cool & Quiet System # 2:

  • (1) Directron Cool mid-tower ATX case
  • (2) Panaflo 80mm L1A case fans (front)
  • (2) Panaflo 92mm L1A case fans (rear and top)
  • (1) Panaflo 120mm L1A case fans (side)
  • (1) PC Power & Cooling Silencer 400 watt PSU
  • (1) Thermalright AX-7 heatsink with Panaflo 80mm H1A
  • (1) Epox 8KHA+ with XP-1800+ @ 1610 MHz

Typical System # 3:

  • (1) Lian Li PC68-USB aluminum mid-tower case
  • (2) Adda 80mm case fans (front)
  • (2) Thermaltake 80mm case fans (back)
  • (1) Thermaltake 92mm case fan (side)
  • (1) Sunon 120 mm case fan (top)
  • (1) PC Power & Cooling Silencer 400 watt PSU
  • (1) Thermalright SK-6 heatsink with Sunon 60mm, 27 CFM fan
  • (1) Epox 8K7A with XP-1800+ @ 1610 MHz

Putting it all together:

RoboTech (Lee Garbutt)

Step #1 – Layout the Fan Locations

Based on the case and the components you will be using, plan where to locate the fans. If your case has provisions for mounting fans, you can use these as a starting point. As a bare minimum, you will want one fan in the front blowing in and another one in the rear blowing out. Mounting additional fans in the front, rear, side and top will provide the airflow needed for excellent case cooling.

Try to keep the airflow reasonably balanced (air in = air out). I like to have a little more air blowing into the case than air blowing out. This will maintain a positive case pressure (helps keep dust out) and makes up for airflow losses caused by intake fan filter/grills. For example:

  • (2) 80mm fans in the front blowing in
  • (1 or 2) 80mm fans on the back blowing out
  • (1) 92mm or 120mm blow-hole on the top blowing out
  • (1 or 2) 92mm or 120mm fans on the side panel blowing in
  • (1 or 2) 80mm fans in the power supply blowing out


Mark the exact center location for each new fan. When laying out the top blow-hole, first mark the areas that will be blocked by the power supply and any CD-ROM drive in the top bay. Then locate the fan in between these two areas to avoid interference. If using more than one side fan, mount one low to bring air into the bottom of the case (prevents a stagnant pocket of warm air forming) and the second one over the video card, Northbridge and RAM area.


Some people like to mount a side fan right over top of the CPU heatsink fan. In theory this makes sense (coolest air straight to the processor) but in my experience sometimes this can actually increase CPU temps a little by disrupting the airflow into the heatsink fan – your case, your choice!

OK, enough talk – let’s get to work!

Step #2 – Strip your case

We need room to work and we don’t want metal shavings trapped in the case, so take the case completely apart. Ideally you are starting with an empty new case. Remove the side panels, front bezel, drive cages, motherboard tray, top, etc. Carefully remove the switches, LEDs, and any plastic fan holder brackets.

RoboTech (Lee Garbutt)

Step #3 – Cut out the fan openings

The first thing we want to do is remove those nasty stamped grills from the case. It is not uncommon for the preformed grills (holes, slots, spiral patterns, etc.) to block 50% or more of the opening. Not only do they restrict airflow, they also generate noise by creating air turbulence.

The hole saw is my weapon of choice for removing stamped grills and cutting new openings for fans. You can also use a Dremel tool, nibbler or whatever tool serves your purpose.

These pictures are a front

and rear view

of the Directron case showing the fan locations for the two front 80mm and one rear 92mm case fans. I decided to measure the actual blockage of the two front openings using a simple machine vision program.


As you can see, 70% of the fan opening is blocked by metal; now you can see why removing these pre-stamped grills is important.


The same thing goes for power supplies too!

Use a hole saw which corresponds to the size of fan you are using. Hole saws can be purchased at numerous hardware outlets, such as Home Depot or ordered online from or I strongly suggest that you securely clamp each piece down as you work on it.


You can use a drill press


for some of the pieces and a hand drill


for the harder to reach areas. In each case, place a heavy board underneath and clamp the case or panel securely down to hold it while cutting. Use a relatively low speed and keep the saw level with the work surface as you go.

Clamping the piece you are drilling will help minimize vibration and chatter, yielding a smoother finished cut. Take care as a hole saw likes to “grab” as it cuts through.

Note: A lot of people believe that for a hole saw to work, there has to be material in the center of the work piece for the pilot hole. An easy way to get around this is to clamp the piece securely to a large board and then just drill the center pilot hole in the board. I have used this technique many times to enlarge an 80mm hole (no center at all) to a 92mm or 120mm hole.

Continue to cut out the openings for all the new fans you are adding to the case. Once again, securely clamp each piece before cutting.

RoboTech (Lee Garbutt)

Step #4 – Deburr the holes

After the large center holes are cut for the fans, use a deburring tool to break all the sharp edges. If you don’t know what I’m talking about, then just use a metal file. As a last step, run a piece of medium-coarse sand paper around the inside to give a smooth finish.

Step #5 – Drill the fan mounting holes

Once all the large fan center holes are finished, it’s time to drill the four mounting screw holes. A 3/16” hole is about right for most mounting hardware (screws or bolts). One way to lay out the corner holes is to use a paper template – just tape it into positions and drill four 3/16” holes.


Another way is to carefully take a fan and square it up over the hole, using the fan body as a template. Mark one corner hole and drill it using a 11/64” drill bit. Put the fan back into position and drop a #8 machine screw through the hole you just drilled to locate that corner.

Now drill the diagonal corner and drop a screw into that hole. (You don’t need to put nuts on the bolts or tighten things down – this is just to hold the fan in position so the other hole locations don’t “walk”.) Drill the remaining two holes and then open all four up to 3/16”. Deburr the mounting holes with a counter sink or file.


Step #6 – Clean the case

Now that we are done sawing and drilling, blow off all the pieces with shop air (you are wearing your safety glasses, right?). Turn the case upside down and bang on the sides to make sure all the metal shavings are removed before starting assembly. Wipe the case and all of the pieces down with a damp cloth.

RoboTech (Lee Garbutt)

Step #7 – Mount the fans

The easiest way to mount fans is to use the self-tapping “fan screws”. Typically these are included with a fan but if not, they can be purchased separately. Since we are using low RPM fans, I am not going to use rubber washers or grommets. These can help reduce vibration and noise on some of the higher speed models.

Double-check each fan as you mount it to make sure the airflow will be going in the right direction! Most fans have a little arrow on the frame indicating the direction of airflow. (The brand logo sticker on the hub is usually on the outlet side.) If it is not marked, hook it up to power and test it to see which way the air blows.

Use wire fan grills to protect all the exposed openings. Install filters/grills on all the fans blowing air in. It is often a good idea to mount a fan grill on a fan’s inside surface as well, to keep wiring and probing fingers out of the rotating fan blades.

Step #8 – Assemble the computer (use whatever procedure works for you)
  1. Install all the drives (DVD-ROM, CD-R/W, FDD, HDDs, etc.)
  2. Install the power supply (check switch is set to proper voltage – 115/220 VAC)
  3. Mount the CPU, heatsink fan, and memory modules onto the motherboard
  4. Install motherboard and connect control wiring (Pwr, Reset, LEDs, Spkr, etc.)
  5. Route and connect all power wiring (drives, fans and mobo)
  6. Route and connect all data cables (IDE, SCSI, audio, etc.)
  7. Install video card

Note: It is very important to neatly bundle and route all wiring and cables inside the PC to minimize blocking and disrupting airflow. Consider “rounded cables” (buy them or make your own) to replace the flat ribbon cables. Wire ties, spiral wrap and plastic loom tubing can also be used to help keep the wiring neat and orderly.

Step #9 – Pre-flight check

Re-check all connections, jumpers and DIP switch settings.

Step #10 – Power-up!

  • Connect the keyboard, mouse and monitor.
  • Connect power cords.
  • Turn ON the computer.

Immediately go into the BIOS setup program, go to the PC Health section and check the CPU temperature. This will either confirm that the HSF is properly seated (if temps are high and rising…) or let you know there is a problem. Also, check out your various motherboard voltages while you are here, just to make sure everything looks OK.



RoboTech (Lee Garbutt)

Final Results

Well, if you have made it this far, you should be relishing in that wonderful absence of noise called quiet! Both of my two cool & quiet test boxes live up to their names. Case temperatures are good and the CPU temperatures are quite acceptable. To make comparing the results more relevant, I used the same processor and operating conditions on all three computers:

  • Athlon XP-1800+ Palomino CPU
  • Slightly overclocked to 1610 MHz (140 MHz FSB x 11.5)
  • Epox 8K7A or 8KHA+ motherboard
  • Default Vcore (1.75 volts)
  • 512 MB DDR RAM
  • GeForce 3 or 4 video card
  • Full load temperatures produced running Folding@Home

So, let’s see how we did:

Cool& Quiet System #1:

Lian Li PC60 aluminum case with (4) Panaflo 80mm and (2) Panaflo 120mm L1A case fans, modified PC Power & Cooling Turbo-Cool 425 watt PSU and Thermalright AX-7 with Panaflo 80mm H1A:

  • 36 dBA Avg at 3’ (oh, yeah!)
  • 24 C ambient room
  • 26 C internal case
  • 38 C CPU full load

Cool& Quiet System #2:

Directron Cool mid-tower ATX case with (2) Panaflo 80mm, (2) Panaflo 92mm and (1) Panaflo 120mm L1A case fans, PC Power & Cooling Silencer 400 watt PSU, and Thermalright AX-7 with Panaflo 80mm H1A:

  • 40 dBA Avg at 3’
  • 24 C ambient room
  • 27 C internal case
  • 39 C CPU full load

“Typical” System #3:

Lian Li PC68 with (4) 80mm & (1) 92mm and (1) 120mm case fans, PC Power & Cooling Silencer 400 watt PSU, and Thermalright SK-6 with Sunon 60mm, 27 CFM fan:

  • 50 dBA Avg at 3’
  • 24 C ambient room
  • 26 C internal case
  • 41 C CPU full load

Note: Internal case and CPU temperatures were taken using onboard sensors using BIOS and MotherBoard Monitor5 and confirmed to be within +/- 2 C using pre-checked DigitalDoc5 temperature probes. (In my experience, the EPoX motherboard temperature sensors have been remarkably accurate.) Sound pressure level readings were taken with a calibrated Extech model 407736 sound level meter. Three readings were taken 3’ from the front and side of the computer and averaged together.

RoboTech (Lee Garbutt)


I was very happy with both the cooling abilities and relative quiet exhibited by the two cool and quiet PCs. The first system is so quiet I can barely tell it is running without walking up to it and “listening”. It’s almost as quiet as my old P-II or PowerMac boxes.

The second cool and quiet system is a little noisier than the first one, primarily due to the power supply running under load. While still quite acceptable, it is slightly more noticeable when walking into my office.

The third, reference system, is much noisier than either of the first two. Now don’t get me wrong – even this rig is no box of hair dryers – at least not any more. I have managed to happily co-exist with it running 24/7 for much of the past year.

A big improvement was made when I replaced the old 1.4 GHz T-Bird chip with a newer XP-1800+. Even at the same clock speed (1,600 MHz) the XP runs cooler, allowing replacement of the old 60mm Delta 37 CFM screamer with a much quieter Sunon 27 CFM fan. After the switch, the CPU temperatures went up a degree or two but the noise dropped from a high pitched 54 dBA to a much more tolerable 50 dBA.

So, this just goes to show that the average PC enthusiast can assemble their own high performance air cooled system with excellent cooling without generating excessive noise. If your cooling needs go beyond the limits of air-cooling (overclocking or high ambient temperatures), then other options await you, including the wonderful world of water-cooling!

I hope you have enjoyed this guide and found it useful for your own project. Good luck!

Be cool… and quiet,

RoboTech (Lee Garbutt)